Very few people would not agree that watermelons are what’s good about summer. A centuries-old vining fruit, it is a member of the Cucurbitaceae family making it a relative of vining vegetables such as pumpkins, squash, and cucumbers. All home-grown watermelons are cultivars of the species known as Citrullus lunatus. This fruit is thought to have originated in Africa’s Kalahari Desert approximately 5,000 years ago and made its way to the United States with the slave trade. Hybridizing has created well over 100 various cultivars that will come in differing shapes, sizes, and sometimes colors.
The characteristic of watermelon is its sprawling and spreading vine that features large hairy lobed foliage. This plant will produce blooms that are bright yellow beginning in the middle of summer. Watermelon fruit develops and will ripen fairly quickly. Harvesting will generally begin at the end of summer and continue into the beginning of autumn. Individual plants can produce as many as four watermelons.
Today, watermelons are divided into four differing groups:
- Smaller icebox melons that can weigh from 5 to 15 pounds
- Picnic watermelons that are large in size and will weigh from 15 to 50 pounds
- Melons with yellow or orange flesh that are known to be exceptionally sweet
- Hybrid seedless melons weighing 10 to 20 pounds
Generally, watermelons are planted directly from seed in garden beds once the ground temperature reaches at least 70°F. If you reside in a cooler area, you can start seeds indoors for later transplanting. They should be started about a month before the projected final frost date. Expect to wait 80 to 90 days and go through different watermelon growing stages for your melons to mature for harvest, although some short-season cultivars exist and need no more than 70 days to enjoy.
Planting Watermelon
Most home gardeners will sow watermelon seeds directly in their garden beds once the final frost has passed. The alternative is to begin seeds indoors in peat pots approximately a month before the final frost date. It is important to sow seeds only when temperatures have stabilized between 70° and 80°F. range because these seeds require warm ground for germination. You can speed the process up a bit by covering the ground with black plastic to warm it faster.
To prepare your garden bed, create mounds that are spaced approximately 5 to 6 feet apart. In each mound, plant a half-dozen seeds an inch deep. If you are using seedlings that you have started indoors or purchased from a nursery, plant two seedlings on every mound.
In cooler regions, it is recommended to use row covers to keep your new little plants warm. These will also give added protection from pests. When flowering begins, row covers must be removed to allow pollination. If you are planting seedless watermelon cultivars, you will need to plant them with a selection of watermelons with seeds to permit pollination, as these hybrids are sterile.
Your crop needs to be kept weed-free during the entire growing season. It is also important for those cultivating watermelon in climates with shorter growing seasons, to snip flowers the final six weeks before the first projected frost date so that the final melons have time to ripen. Again, row covers may be a good alternative to protect your melons toward the end of the season.
As the melons develop and increase in size, it’s wise to set them on a small bed of straw to prevent rot and various pests.
Soil
Rich fertile soil that is well-draining is ideal for watermelon cultivation so amend the soil bed before planting with compost and lots of organic matter. The soil pH should be a little acidic to neutral measuring between 6.0 and 6.8.
Light
Full exposure to sunlight is necessary for your crop to thrive and for sugars to develop. The plants will tolerate limited shade if the climate is especially hot, but too much shade risks reducing the size and number of melons produced.
Water and Humidity
As the name suggests, these plants do require regular watering, particularly when transplanting seedlings. Once fruits appear, you can reduce watering unless the climate is very hot and very dry. Because the root system of watermelons moves fairly deeply, they will tolerate a little dryness as long as it is short-lived. Do not overwater, or they will lose some of their sweetness.
If your area is humid, that’s fine because this fruit will manage. Soil moisture must be retained.
Temperature
Climates with temperatures in the 80s Fahrenheit or higher are ideal.
Feeding
Watermelons like to feed, so soil bed preparation before planting is crucial. If you are unable to amend your soil, consider using a slow-release fertilizer at the beginning of the growing season and then side-dress your plants again in the middle of the season with compost.
If your only choice is to use a synthetic chemical fertilizer, select one (NPK) for the beginning of the growing season that is higher in nitrogen than in phosphorous or potassium to encourage vine and foliage growth. Once your plants begin to bloom, fertilize a second time but this time with an NPK fertilizer that is lower in nitrogen to stimulate fruit growth.
Watermelon Pests, Diseases, and Problems
The greatest danger to your watermelon crop will be the cucumber beetle. If you use row covers, chances are you will prevent a good number of them from invading your crop. Other pests that will enjoy feasting on your fruit include aphids, mites, and vine borers.
Diseases that can infect your crop include
- Alternaria Leaf Spot
- Anthracnose
- Blossom-end Rot
- Fusarium wilt
- Gummy Stem Blight
- Powdery mildew
If these diseases are common to your area, consider cultivating varieties that are disease resistant. To prevent mildew, avoid overhead watering in favor of watering at the base of the plant.
Harvesting Watermelons
The greatest challenge to harvesting watermelon is deciding if it is adequately ripe. When preparing for harvest, note that riper melons will have a duller outer rind and you will not be able to pierce it with a fingernail, while the vine tendrils near the fruit will turn brown. Also, the part sitting on the surface will not be light green but will appear yellow. You can also thump it to hear if it sounds hollow to know if it is ripe.
Watermelons should be enjoyed immediately upon harvesting. Sliced watermelon will keep in the refrigerator for several days. It is unwise to store uncut watermelons in a refrigerator, better in a cooler storage room with a temperature no higher than 50°F. where they will keep for up to two
weeks.
Watermelon Varieties
Long-season cultivars that require 80 to 90 days
- Ali Baba – 12 to 30 lbs., oblong in shape with red flesh
- Moon and Stars – this hybrid offers both red and yellow-fleshed cultivars
Short-season cultivars
- Blacktail Mountain – 6 to 12 lb. red-fleshed melons with dark green outer rinds
- Sugar Baby – red-fleshed melons that weigh 6 to 10 lbs.
Seedless cultivars
- Super Seedless – 16 to 20 lb. melons with red flesh; they need 90 to 95 days to harvest
- SweetBite – 5 to 8 lb. red-fleshed melons that require approximately 75 days to harvest
If you need one fruit to represent summer, choose watermelon.